Wrinkle resistance finishes for cotton fabric using citric acid derivatives for soil release

ABSTRACT

A process for producing wrinkle-resistant cotton fabric that does not increase the difficulty of laundering; said process comprises the addition of citric acid or monoesters of citric acid to the usual finishing formulations containing a crosslinking agent for cellulose with or without a softening agent.

United States Patent 191 Frick, Jr. et a1.

WRINKLE-RESISTANCE FINISHES FOR COTTON FABRIC USING CITRIC ACID DERIVATIVES FOR SOIL RELEASE Inventors: John G. Frlck, Jr., New Orleans;

Wilson A. Reeves, Metairie; Andrew G. Pierce, Jr., New Orleans; Gloria A. Gautrelux, Metairie, all of La.

The United States of America as represented by the Secretary of Agriculture, Washington; DC.

Filed: Nov. 5, 1971 Appl. No.: 196,213

Assignee:

8/185, 8/187,117./139.4, 38/144 Int. C1.D06m 15/54, D06m 15/56, D06m 15/58 Field of Search 8/115.6, 182, 184, 8/185, 187

US. Cl. 8/l15.6,.'8/182, 8/184,

[ Aug. 28, I973 Primary Examiner-George F. Lesmes Assistant Examiner-J. Cannon Attorney-R. Hoffman et al.

ABSTRACT A process for producing wrinkle-resistant cotton fabric that does not increase the difficulty'of laundering; said process comprises the addition of citric acid or monoesters of citric acid to the usual finishing formulations containing a crosslinking agent for cellulose with or without a softening agent.

6 Claims, No Drawings WRINKLE-RESISTANCE FINISHES FOR COTTON FABRIC USING CITRIC ACID DERIVATIVES FOR SOIL RELEASE A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention is the field of finishing cotton fabric for the introduction of wrinkle resistance and the related durable-press properties and for the introduction of soil release. The invention provides a process for finishing cotton fabric that imparts wrinkle resistance but does not increase the tendency of the fabric to retain soil.

Finishes have been developed that impart to cotton fabric the ability to resist wrinkling and to dry smooth after laundering. These are the wrinkle-resistance and durable-press finishes. Among the disadvantages of these finishes, however, is that they also impart an increased tendency for the fabric to retain soil. After finishing the fabric retains soil with a greater tenacity and is, therefore, more difficult to clean by laundering.

The finishing of cotton fabric for wrinkle resistance usually consists in the application of crosslinking agent with appropriate catalyst and softener, and in following the application with drying ahd heating to promote a cellulose crosslinking reaction on the fabric. The crosslinking has some effect toward increasing soil retention, and the softening agent has an additional effect. To counteract the increased soil retention, soil release agents have been incorporated in the finishing formulation. These soil release agents are usually copolymers containing ionic groups such as described by F. W. Marco in U. S. Pat. No. 3,377,249 and by H. E. Bille,

A. Echell, and G. A. Schmidt in Textile Chemist and Colourist, Vol. 1, 1969, pages 600-607. Presumably, these agents are merely deposited on the surface of the fiber or yarn. Durability of the deposited polymer depends on the insolubility of the polymer and reaction of the polymer with itself to form a crosslinked network. To get the necessary effectiveness and durability with these agents and to avoid excessive stiffness, these copolymers must be prepared carefully.

The object of this invention is to provide a finishing process for producing wrinkle-resistant and durablepress cotton fabric that has improved soil release properties and is therefore more readily cleaned by laundering. The fabric finished by this process has a wrinkle resistance equivalent to that produced by presently available conventional treatments and has a soil releasing ability approaching that of untreated cotton.

The objective of this invention is accomplished by modifying a conventional finishing formulation with the addition of 0. l$.0% citric acid or citrate monoester with a small or moderate size aliphatic carbon chain. Examples of citrate esters that may be used are monomethyl citrate, monoethyl citrate, mono-butyl citrate, and mono-( 2-ethylhexyl)citrate. Citrates of long chain alcohols, such as monooctadecyl citrate, are ineffective or, indeed, may be detrimental to soil releasing properties. The citric acid derivative is dissolved or emulsified in the treating formulation, and the remainder of the formulation is only slightly modified from the conventional formulation. Cotton fabric is treated with formulation containing the citric acid derivative by conventional procedures. The fabric is impregnated with the formulation, dried, and heated to cure" the finish or promote reaction of the crosslinking agent.

Essentially the process of this invention seems to increase soil release by increasing the hydrophil icity of the fiber surface through introduction of carboxyl groups. The process uses only simple monomer compounds as additives to a conventional process. In contrast, previous processes for the purpose require rather complicated copolymers. Also, since the citric acid derivatives used in this invention contain reactive hydroxyl groups as the cellulose does, they can be chemically bound to the cellulose by the crosslinking agent. Such reaction will contribute to the durability of the finish.

The formulation used in the practice of this invention will contain 5-15% of a polymethylol crosslinking agent dissolved in water to impart wrinkle resistance. These agents can be one of those currently used in textile. finishing. Examples of these are dimethylol urea, dimethylol ethyleneurea, dimethylol dihydroxyethyleneurea, and dimethylol methyl carbamate. To increase the soil releasing property of the finished fabric, the formulation will contain also 0. l-5.0% of citric acid or a monoester of citric acid either dissolved or emulsified in the aqueous medium.

In addition to the above ingredients, the formulation will contain 0.1-1 .0% of an acidic metal salt to serve as catalyst for the reaction of the crosslinking agent with cellulose and with the citric acid derivative. Magnesium chloride and zinc nitrate are suitable salts for this purpose. The concentration of catalyst is less than used in conventional finishing treatments because the citric acid derivative has an activating effect on the salt and reduces the quantity required. When desired, one of the usual softening agents can be included in the formulation. Usually this will be 02-10% of a polymer such as polyethylene or a polyacrylate.

The formulation described is applied to cotton fabric in the usual manner. The fabric is impregnated with the formulation by soaking the fabric and padding to remove excess. The formulation left on the fabric amounts to 60-90% of fabric weight. The fabric is then dried in hot air and heated or cured at l20-l C for 1-5 minutes to effect reaction of the finishing agent. The fabric may then be washed to remove excess agents and residual catalyst.

The treated fabric shows a degree of wrinkle resistance equal to that of a similar fabric given a conventional wrinkle-resistance treatment, that is, a treatment without the citric acid derivative. The treated fabric shows no more tendency to retain soil than the original fabric before treatment.

The treatment and the properties of the finished cotton fabric are illustrated by the following examples. In these examples, the ingredients of the formulations applied to the fabric are measured as percent of total formulation weight. Fabrics were tested for wrinkle recovery by the recovery angle method and for soil release by the oily stain release method. Both methods are among those developed by the American Association of Textile Chemists and Colorists and are described in the 1969 Technical Manual of the AATCC. Fabric was also tested for tearing resistance by the Elmendorf method of the American Society for Testing Materials and described in the ASTM Standards for Textile Materials.

Example 1 A series of formulations was prepared containing l% dimethylol ethyleneurea and the following components dissolved or emulsified in water.

Formulation A: 2.5% magnesium chloride hexahydrate.

Formulation B: 0.2% magnesium chloride hexahydrate and 0.3% citric acid.

Formulation C: 0.2% magnesium chloride hexahydrate and 2.0% 2-ethylhexyl citrate.

Formulation D: 0.2% magnesium chloride hexahydrate and 5.0% 2-ethylhexyl citrate.

Formulation E: 0.2% magnesium chloride hexahydrate and 2.0% butyl citrate. Cotton printcloth was padded with the above formulations, dried for 7 minutes at 60 C, cured for 3 minutes at 140 C, and washed. The treated fabrics had the following properties:

Formulation Wrinkle re- Soil release Tearing applied covery angle rating after resistance (degrees, washing at (grams, W F) 60 C W) None (untreated fabric) 186 3 .4 1007 A 273 2.5 520 B 283 3.3 513 C 276 3.5 493 D 290 3.3 507 E 279 3.2 507 The data show that the crosslinking treatment without citrate, formulation A, reduces the soil release rating from that of the untreated fabric. Addition of citrate to the formulation returns the soil release rating to about the original level. This is accomplished with essentially no loss in wrinkle resistance and no further loss of tearing resistance.

Example 2 A series of formulations was prepared containing 10% dimethylol ethyleneurea and the following components dissolved or emulsified in water.

Formulation F: 2.5% magnesium chloride hexahydrate.

Formulation G: 2.5% magnesium chloride hexahydrate and 0.5% polyethylene.

Formulation H: 0.2% magnesium chloride hexahydrate, 0.5% polyethylene, and 2.0% 2-ethylhexyl citrate. 4

Formulation J: 0.2% magnesium chloride hexahydrate, 0.5% polyethylene, and 2.0% butyl citrate. Cotton printcloth was padded with the above formulations, dried 7 minutes at 60 C, cured 3 minutes at C, and washed. Test results on the fabrics are as follows:

Wrinkle recovery Soil release Formulation angle rating after applied (degrees, W+F) washing at 60C None (untreated fabric) l8l 3.5 F 280 2.9 G 299 1.5 H 289 3.4 J 286 3.6

The soil release ratings show that the addition of citrate to the formulations increases the ease of soil release in the treated fabric to the level in the untreated fabric even when the treatment contains polyethylene, an agent that produces a large adverse effect.

We claim:

1. A process for producing wrinkle-resistant cotton fabric without reducing the ease of soil removal which process comprises:

a. adding to a conventional crosslinking bath, containing a softener, about 0.1 to 5.0 weight percent of a mono-ester of citric acid selected from the group consisting of monobutyl citrate and 2- ethylhexyl citrate,

b. impregnating a cotton fabric in the crosslinking bath from (a),

c. drying and curing the impregnated fabric from (b).

2. The process of claim 1 wherein the monester of citric acid is monobutyl citrate.

3. The process of claim 1 wherein the monoester of citric acid is Z-ethylhexyl citrate.

4. A process for producing wrinkle-resistant cotton fabric without reducing the ease of soil removal which process comprises:

0. adding to a conventional crosslinking bath about 0.1 to 5 .0 weight percent of a monoester of citric acid selected from the group consisting of monobutyl citrate and 2-ethylhexyl citrate,

b. impregnating a cotton fabric in the crosslinking bath from (a),

c. drying and curing the impregnated fabric from (b).

5. The process of claim 4 wherein the monoester of citric acid is monobutyl citrate.

6. The process of claim 4 wherein the monoester of citric acid is 2-ethylhexyl citrate. 

2. The process of claim 1 wherein the monester of citric acid is monobutyl citrate.
 3. The process of clAim 1 wherein the monoester of citric acid is 2-ethylhexyl citrate.
 4. A process for producing wrinkle-resistant cotton fabric without reducing the ease of soil removal which process comprises: a. adding to a conventional crosslinking bath about 0.1 to 5.0 weight percent of a monoester of citric acid selected from the group consisting of monobutyl citrate and 2-ethylhexyl citrate, b. impregnating a cotton fabric in the crosslinking bath from (a), c. drying and curing the impregnated fabric from (b).
 5. The process of claim 4 wherein the monoester of citric acid is monobutyl citrate.
 6. The process of claim 4 wherein the monoester of citric acid is 2-ethylhexyl citrate. 